Near-infrared imaging observations of the southern massive star-forming region G333.6−0.2     

Takuya Fujiyoshi  Craig H. Smith  Toby J. T. Moore  Stuart L. Lumsden  David K. Aitken  Patrick F. Roche 《Monthly notices of the Royal Astronomical Society》2005,356(3):801-809

We present near-infrared broad-band JHK ' images of the southern massive star-forming region G333.6−0.2. The slope of the K -luminosity function towards the region  (0.24 ± 0.01)  is considered to be equivalent to that expected for main-sequence stars in the solar neighbourhood. Point sources with their ( H − K ) colour greater than 1 are more likely to be located in extended emission and it is suggested that these objects are physically associated with the H  ii region.  相似文献   

Infrared polarimetry of the southern massive star-forming region G333.6−0.2     

Takuya Fujiyoshi  Craig H. Smith  Christopher M. Wright  Toby J. T. Moore  David K. Aitken  Patrick F. Roche 《Monthly notices of the Royal Astronomical Society》2001,327(1):233-243

We present     spectropolarimetry, and 12- and 2-μm imaging polarimetry of the southern massive star-forming region G333.6−0.2. Spectro-polarimetry measurements show that the polarization observed towards the nebula contains a mixture of both absorptive and emissive polarizations. Model fitting to the spectra indicates that the temperature of the mid-infrared emitting dust grains is generally ∼200 K and the optical depth of the absorbing dust at 9.7 μm is ∼1.5. Fits are also made to the polarimetry spectra, which show a reasonably constant peak absorptive polarization (∼3.4 per cent at 43°) across the face of the H  ii region. This absorptive polarization position angle is consistent with that found by the 2-μm imaging polarimetry     and is most likely due to the Galactic magnetic field local to G333.6−0.2. When the absorptive polarization is subtracted from the 12-μm polarization image, the emissive polarization pattern that is intrinsic to the star-forming region is revealed. A probable magnetic field configuration implied by the intrinsic polarization suggests star formation initially influenced by the Galactic magnetic field which is eventually perturbed by the star formation process.  相似文献   

Vertical structure, turbulent mixing and fluxes during Lagrangian observations of an upwelling filament system off Northwest Iberia     

E. D. Barton  M. E. Inall  T. J. Sherwin  R. Torres 《Progress in Oceanography》2001,51(2-4)

In August 1998, a recurrent filament located near 42°N off Galicia was sampled as part of the OMEX-II project. Lagrangian and other observations were made on the shelf where the filament arose and offshore in the filament itself under upwelling favourable but fluctuating winds. The shelf drift experiment monitored a change from southward to weak northward net flow as the winds decreased to zero. Shipborne ADCP measurements showed that the shelf was supplying decreasing volumes of water to the filament as the wind speeds decreased. At the shelf edge the internal tide was larger than can be explained by local forcing and there were many unusually large high frequency internal waves with a quasi-sinusoidal form. Turbulence observations revealed enhanced dissipation rates and vertical eddy diffusion coefficients within the shelf thermocline (of order 1 cm² s⁻¹), which appeared to be caused by the breaking of internal wave. A second Lagrangian experiment was executed in the filament some 120 km offshore, which again coincided with a period of wind relaxation. Cross-sections revealed a double cold core and that the offshore flow was limited to a thin surface layer. Substantial onshore flow occurred below 50 m in the centre of the filament, while the strongest and deepest offshore flow coincided with its northern boundary. Turbulent kinetic energy dissipation rate measurements showed very weak mixing below 15 m in the filament core, but enhanced mixing at its boundaries. Four mixed layer drifters released in the filament initially indicated convergence at its southern boundary, marked by strong temperature and salinity contrasts. After the wind became more favourable for upwelling, the drifters accelerated. One drifter traced the full extent of the filament, while the other three escaped from it and began to circulate cyclonically over 28 days in a 100 km diameter loop back towards their release point. Although strong mesoscale activity linked the shelf and ocean regimes, offshore transport in the filament was weak at the time of the experiment and vertical and horizontal re-circulations on a variety of time scales were important. There was sufficient vertical mixing in the thermocline to cause it to thicken and draw some heat into the lower layers during the summer months on the shelf. The amount of heat involved was too little to have a significant impact on the development of a filament over a typical lifetime of a week.  相似文献   

Release test with electromagnetic seismograph     

Vladimír Tobyáš  Reviewer J. Buben 《Studia Geophysica et Geodaetica》1979,23(4):322-332

u¶rt; am ¶rt; mua maum aa nu ¶rt;uu ma n¶rt;a mnu ma auau am. a¶rt;¶rt;a mu m¶rt; auu a¶rt;am n¶rt;um m nm aa u n uu naua nu¶rt;a ma uuaama aumam ma nm aa u uu uuma u.  相似文献   

Sensitivity of the Sharpe and Worden gravity meters to vertical motion     

Vladimír Tobyáš  Karel Diviš  Reviewer O. Novotný  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1979,23(2):122-130

Summary Using the least-squares method the constants of both gravity meters — seismometers — were derived from the amplitude responses, observed under vertical motion on a vibrating table in the 0.3–30 s range. The values of the seismogram amplitudes, above which seismic waves cause an observable displacement of the gravity meter reading beam, were determined for the SKD and Press-Ewing station seismographs.  相似文献   

Estimate of the effect of vibrations on quartz gravity meters     

Vladimír Tobyáš  Karel Diviš  Reviewer M. Pick 《Studia Geophysica et Geodaetica》1978,22(4):336-347

Summary Relations for computing the minimum amplitudes of ground vibrations which generate oscillations of the gravity meter reading beam at the limit of the resolution of the optical system, have been derived. The minimum amplitudes in the ground displacement period range of0.1 to10 s, for the assumed values of the fundamental parameters of quartz gravity meters (i.e. the periods and damping constants of the pendulum and the mechanico-optical magnification of the pendulum deflections), range from tenths of a micrometre to units of micrometres. Larger displacement amplitudes, due to, e.g., earthquakes and traffic, disrupt gravity measurements.  相似文献   

Amplitude characteristics of the first maximum of broad-band electromagnetic seismographs excited by harmonic motion     

Vladimír Tobyáš 《Studia Geophysica et Geodaetica》1968,12(1):28-37

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Contribution to the investigation of small intermediate-depth earthquakes in the Vrancea region     

Cornelius Radu  Vladimír Tobyáš 《Studia Geophysica et Geodaetica》1968,12(4):402-406

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Rheological modelling of measuring systems of quartz gravity meters     

Jiří Trešl  Reviewer V. Tobyáš 《Studia Geophysica et Geodaetica》1985,29(2):120-126

Summary Some phenomena, recorded during pressure tests of quartz gravity meters, are studied theoretically using a model of the visco-elastic continuum. Expressions, describing the response of the measuring system as a function of the time variation of pressure disturbances, are derived by solving the appropriate rheological equations.

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n ¶rt;u n uu u¶rt; u, uu uu unu ¶rt;u u. u u uu u ¶rt; u nuu u uu u uuu ¶rt; u ¶rt;u.

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The effect of the magnetic field on the accuracy of measurements with Worden and Sharpe gravity meters     

Karel Diviš  Vladimír Tobyáš  Reviewer Z. Šimon 《Studia Geophysica et Geodaetica》1976,20(4):338-345

Summary The effect of an additional homogeneous magnetic field with an intensity of 0–4.5 Oe on the Worden quartz gravity meter No. 961 and on Sharpe quartz gravity meters Nos 173 and 174 was tested. Whereas no effect was observed with the Worden gravity meter, the magnetic field had a measurable effect on both the Sharpe gravity meters. The largest deviation of the reading beam is caused by the horizontal component of the magnetic field which acts in the plane of oscillation of the gravity-meter arm. The Sharpe gravity meter No. 173 is considerably sensitive; a field of 0.2 Oe intensity, corresponding to the magnitude of the horizontal component of the geomagnetic field in mid-latitudes, causes an error in the measurement of gravity of as much as 0.08 mGal. With a view to the different behaviours of the individual quartz gravity meters of the same type in a magnetic field, it should prove expedient to carry out check measurements with all gravity meters and, with regard to the sensitivity of the gravity meter to the magnetic field and the required accuracy of the gravity determination, take into account this perturbing factor in field measurements, as well as laboratory tests of gravity meters.  相似文献